Control valve and system

ABSTRACT

A control valve for use in a hydraulic brake system having a pressure source and a pressure responsive brake is provided with a pair of proportioning members in series flow relation which respectively proportion the fluid pressure supplied from said source to said brake. One of the proportioning members is actuated in response to supplied fluid pressure from the source in excess of a predetermined value to effect the application of a proportionally reduced pressure to the brake, and the other of the proportioning members is actuated in response to the proportionally reduced pressure of another predetermined value predeterminately in excess of the first named predetermined value to further proportionally reduce the pressure applied to said brake.

United States Patent Bueler ..303/6 C 101:: I I I with 39 a 5 Kg 15]3,697,138 Marting [4 1 Oct. 10, 1972 [54] CONTROL VALVE AND SYSTEMFOREIGN PATENTS OR APPLICATIONS Inventor: Paul g, Ballwin, 997,7271/1952 France ..73/203 [73] Assignee: Wagner Electric Co ration Newark,rpo Primary Examiner-Milton Buchler Assistant Examiner.lohn J.McLaughlin [22] Flled: May 1970 Attomey-Joseph E. Papin [21] App]. N0.:35,823

' v [57] ABSTRACT [52] US. Cl. ..303/6 C, 60/545 E, l37/505.l2, Acontrol valve for use in a hydraulic brake system 188/349 having apressure source and a pressure responsive [51] Int. Cl. ..B60t 8/26,B60t 11/34 brake is provided with a. pair of proportioning mem- [58]Field of Search.....303/6 C, 22 A; 188/345, 349; bers in series flowrelation which respectively propor- 60/5 -5 137/505, 505-1 tion thefluid pressure supplied from said source to 73/203 said brake. One ofthe proportioning members is actuated in response to supplied fluidpressure from the [56] References C'ted source in excess of apredetermined value to effect the application of a proportionallyreduced pressure to the UNITED STATES PATENTS brake, and the other ofthe proportioning members is 3,155,107 11/1964 Woodford ..137/218 atuated in response to the proportionally reduced Stelzer X pressure ofanother predeten'nined value predeter- St-elZel' C minately in excess ofthe first named predetermined Mllst?r value to further proportionallyreduce the pressure ap 3,385,637 5/1968 Kerstmg ..303/6 C plied to saidbrake 3,462,201 8/1969 Lewis et a1. ..303/6 C 3,508,792 4/ 1970 30Claims, 2 Drawing Figures 1000 IIII PATENTEDncI 10 I972 PAUL G. MARTINGR O T N E V N INPUT PRESSURE FIG. 2

tioning the pressure of said system under preselected conditions.

SUMMARY In the past, various types of control valves have been utilizedin a hydraulic brake system to provide a twostep or double-knee pointproportioning of the fluid pressure supplied from the fluid pressuresource to energize the vehicle rear brakes in order to allow the actualfront brake to rear brake torque distribution to approach thetheoretical or ideal torque distributions therebetween. One of thedisadvantageous features of such past control valves was that thetwo-step or double-knee point proportioning was accomplished byeffecting an area change on the proportioning piston at a predeterminedfluid pressure which necessitated somewhat complex valving and usuallyresulted in complex tolerance and concentricity manufacturing problems.

The principle object of the present invention is to provide a controlvalve for effecting double knee point proportioning which overcomes theaforementioned disadvantageous or undesirable features, and this, aswell as other objects and advantageous features of the presentinvention, will become apparent hereinafter.

Briefly, the present invention embodies both a fluid pressure systemhaving a fluid pressure source and a fluid pressure responsive brake andalso a control valve for said system wherein said control valve includesa pair of modulating means for controlling the application to saidbrakes of pressure supplied from said source with one of said modulatingmeans being generally operable in response to fluid pressure in excessof a predetermined value to perform a fluid modulating operation thereonfor varying the pressure immediately upstream thereof and with the otherof said modulating means being operable generally in response to thevaried pressure in excess of another predetermined valuepredeterminately in excess of the first named predetermined value toperform a fluid modulating operation thereon for also varying thepressure immediately upstream thereof.

RELATED PATENTS This patent application is related to US. Pat.application Ser. No. 730,101 filed May 17, 1968, by Edward J. Falk, saidapplication being assigned to the common assignee of this patentapplication which is a patentably distinct improvement.

DRAWING DESCRIPTION In the drawings which form a part of thespecification and wherein like numerals refer to like parts wherever 60Referring now to the drawings in detail and in particular to FIG. 1, abrake system 1 is provided with an operator actuated master cylinder 2of a type well known in the art which is connected by a conduit 3 tovehicle front brakes 4, and another conduit 5 is interconnected betweenthe conduit 3 and the inlet port of a control or proportioning valve 6.The outlet port of the control valve 6 is connected by a conduit 7 tothe vehicle rear brakes 8.

The control valve 6 is provided with a housing 9 having stepped bores10, 11 and 10a, 11a coaxially aligned therein with stepped counterbores12, 13 and 12a, 13a, respectively. Shoulders or abutrnents 14, areprovided on the housing 9 between the bores and counterbores 11, 12 and11a, 12a, and other shoulders or abutments 15, 15a are provided on thesaid housing between the counterbores 12, 13 and 12a, 13a, respectively.The housing counterbores 13, 13a are closed by closure members or endplugs 16, 16a threadedly received therein, and said closure members areprovided with stepped bores 17, 18 and 17a, 18a which have shoulders 19,19a therebetween, respectively. Annular seals 20, 20a are provided insealing engagement with'the closure member stepped bores 18, 18a andseated against the shoulders 19, 19a about the smaller stepped bores 17,17a, and annular spring retainers 22, 224 are positioned in abuttingengagement between the interior ends of the closure members 16, 16a andthe housing shoulders 15, 15a, respectively. An inlet port 23 whichreceives the conduit 5, as previously mentioned, is provided in thehousing 9 intersecting with the housing counterbore 12 adjacent to themid-portion thereof, and an outlet port 24 which receives the conduit 7,as previously mentioned, is also provided in said housing intersectingwith the housing stepped bore 11a. A connecting passage 25 is providedin the housing 9 having one end connecting with the housing stepped bore11 while the other end thereof intersects with the housing counterbore12a adjacent the leftward end thereof.

Modulating or proportioning members, such as the pistons indicatedgenerally at 26, 26a, are provided with head portions 27, 27a integrallyformed between opposed reduced extensions or stem portions 28, 29 and28a, 29a, respectively. The extensions 28, 28a and 29, 29a are slidablyand guidably received in the housing bores 10, 10a and the closuremember bores 17,

0 17a, said extensions 29, 29a extending through the closure memberseals 20, 20a in sealing engagement therewith, and said extensions 28,28a are provided with free end portions 30, 30a for abutting engagementwith the end walls of the housing bores 10, 10a, respectively. Meteringor proportioning springs 31, 31a are biased between the proportioningpiston head portions 27, 27a and the retainers 15, 15a normally urgingthe proportioning pistons 26, 26a toward their normal or inoperativepositions engaging the free end portions 30, 30a thereof with the endwalls of the housing bores 10, 10a, respectively. It should be notedthat the precompressed force F of the spring 31 is predeterminately lessthan the precompressed force F, of the spring 31a.

The proportioning pistons 26, 26a are provided with annular valvemembers 32, 32a thereon between the head portions 27, 27a and theextensions 28, 28a which, in the inoperative positions of saidproportioning pistons, are spaced from cooperating valve seats, 33, 33aprovided about apertures 34, 34a extending axially through seatingmembers, indicated generally at 35, 35a. The seating members 35, 35a arenormally positioned in seating engagement with the housing shoulders 14,14a, and the seating member apertures 34, 34a are radially spaced fromthe periphery of the proportioning pistons 26, 26a, respectively.Peripheral lip portions 36, 36a are integrally provided on the seatingmembers 35, 35a normally in sealing engagement with the housingcounterbores 12, 12a to close return flow passages 37, 37a providedacross said seating members.

A flow passage, indicated generally at B, is provided in the housing 9connecting the proportioning pistons 26, 26a in series flow relationbetween the inlet and outlet ports 23, 24, said flow passage beingdefined by the counterbore 12, the seating member aperture 34, the bore11, the connecting passage 25, the counterbore 12a, the seating memberaperture 34a and the bore 11a. Of course, it is apparent that thehousing counterbores 12, 12a between the seating members 35, 35a andclosure member seals 20, 20a define inlet chambers 38, 38a in thehousing 9, and the stepped bores 10, 11 and a, 11a define outletchambers 39, 39a in said housing wherein the seating member apertures34, 34a are interconnected between the inlet and outlet chambers 38, 39and 38a, 39a, respectively. The inlet and outlet chambers 38, 39a areconnected in pressure fluid communication with the inlet and outlet port23, 24 at all times, and the connecting passage 25 connects the outletchamber 39 with the inlet chamber 38a at all times.

It should be noted that the proportioning pistons 26, 26a are providedwith substantially equal effective areas A,, A,,, defined by the sealingengagement of the proportioning piston extensions 29, 29a with theclosure member seals 20, a and subjected to the atmosphere in theclosure member stepped bores 17, 17a at all times, and the sealingengagement between the proportioning piston valve members 32, 32a andthe seating member valve seat 33, 33a, as discussed hereinafter, definesubstantially equal effective areas A A on said proportioning pistonswhich are subjected to the fluid pressure in the outlet chambers 39,3911, respectively. The areas A A are predeterminately greater than theareas A,, A,,,

In the operation with the component parts of the system 1 and controlvalve 6 positioned as shown in the drawings and as describedhereinabove, a supplied or input fluid pressure P is transmitted uponoperator actuation of the master cylinder 2 through the conduit 3 toeffect energization of the vehicle front brake 4. The input fluidpressure P also flows from the conduit 3 through conduit 5, the inletport 23 of the control valve 6, the inlet chamber 38, the seating memberaperture 34, the outlet chamber 39, the connecting passage 25, the inletchamber 38a, the seating member aperture 34a, and the outlet chamber 39ato the outlet port 24, and therefrom through conduit 7 to effectenergization of the vehicle rear brake 8 substantially simultaneouslywith the aforementioned energization of the front brake 4. The inputfluid pressure P acts on the effective area A, of the proportioningpiston 26 to establish a closing force PA, tending to urge saidproportioning piston against the compressive force F c of the meteringspring 32; however, the metering spring force F, opposes movement ofsaid proportioning piston until the input fluid pressure P attains apredetermined value R as shown on the line ORT in the graph of P16. 2.When the predetermined value R of the input fluid pressure P isattained, the closing force PA, overcomes the compressive force F of themetering spring 31 to move the proportioning piston 26 rightwardly fromits inoperative position toward an isolating position. The movement ofthe proportioning piston 26 to its isolating position engages the valvemember 32 with the sealing member valve seat 33 closing the sealingmember aperture 34 to isolate the input fluid pressure P in the inletchamber 38 from the output fluid pressure P, in the outlet chamber 39,and upon the engagement of the said valve member with said valve seat,the input fluid pressure P acts on the effective input area A -A, of theproportioning piston 26 to establish an input force which is additive tothe spring force F, to substantially balance the opposed output force PA established by the output fluid pressure P,, acting on the effectiveoutput area A of said proportioning piston.

From the graphical representation in FIG. 2, it is obvious that anincrease in the magnitude of the input fluid pressure P in excess of thepredetermined value R, as shown by the line ORT, will result inproportionally reduced increases in the output fluid pressure P, asshown by the line RU. For instance, when the input fluid pressure P isincreased to a value in excess of the predetermined value R and lessthan the predetermined value U, the input force P (Ar/4,) iscorrespondingly increased and additive to the metering spring force F toovercome the output force P A therefor, the metering piston 26 is movedin a leftwardly direction toward a metering position disengaging thevalve member 32 thereof from the seating member valve seat 33 to effecta metered application of the input fluid pressure P through the seatingmember aperture 34, the outlet chamber 39, the connecting passage 25,the inlet chamber 38a, the seating member aperture 34a, the outletchamber 28a, to the outlet port 24 to effect a proportional increase ofthe output fluid pressure P, in a predetermined ration with the inputfluid pressure P at the inlet port 23, as shown by the line RU in thegraph of FIG. 3 wherein Of course, the increased output fluid pressureP, effects a corresponding increase in the output force P A and when theincreased output force P,,A attains an increased value substantiallyequal to that of the increased input force P(A -A,) and the additivemetering spring force F the proportioning piston 26 is again movedtoward its isolating position to re-engage the valve member 32 with theseating member valve seat 33 to again isolate the increased input fluidpressure P and the increased output fluid pressure P It is, of course,obvious that the proportioning piston 26 will be responsive to furtherincreases in the input fluid pressure P to effect further correspondingproportional increases in the output fluid pressure P in the same manneras previously described.

Of course, the output fluid pressure P also acts on the effective areaA, of the proportioning piston 26a to establish another closing force PA urging said proportioning piston against the compressive force F, ofthe metering spring 31a; however, the metering spring force F, preventsmovement of said proportioning piston until the output fluid pressure P,exceeds the predetermined value U, as shown on the line RUV in the graphof FIG. 2. When the predetermined value U is attained, the closing forceP A overcomes the compressive force F, of the metering spring 31a tomove the proportioning piston 26a leftwardly from its inoperativeposition toward an isolating position. The movement of the proportioningpiston 26a to its isolating position engages the valve member 32a withthe seating member valve seat 33a closing the seating member aperture34a, to isolate the output fluid pressure P, in the inlet chamber 38afrom the output fluid pressure P, in the outlet chamber 39a, and uponthe engagement of said valve member with said valve seat, the outputfluid pressure P, in said inlet chamber acts on the effective input areaA ,-A 0f the proportioning piston 26a to establish another input forceP,(A ,A additive to the spring force F, to substantially balance theoutput fluid pressure in the outlet chamber 39a, hereinafter referred toas Por for claritys sake, which acts on the effective area A inopposition to the input force P,(A 111)- From the graphicalrepresentation in FIG. 2, it is obvious that increases in the magnitudeof the fluid pressure P0 in excess of the predeterminedv value U willresult in a further proportionally reduced increase in the output fluidpressure Por, as shown by the line UV. For instance, when the fluidpressure P0 is increased to a value in excess of the predetermined valueU, the input force P,(A ,-A is correspondingly increased and additive tothe metering spring force PS to overcome the output force Por Atherefore, the proportioning piston 26a is moved rightwardly toward itsmetering position disengaging the valve member 33a thereof from theseating member valve seat 32a to effect a metered application of theincreased fluid pressure P, through the seating member aperture 34a andthe outlet chamber 39a to the outlet port 24 to effect a proportionalincrease of the output fluid pressure Por in a predetermined ratio withthe fluid pressure P, in the inlet chamber 38a, as shown by the line UVin the graph of FIG. 3 wherein Of course, the increased output fluidpressure For effects a corresponding increase in the output force Por Aand when the increased output force Por A attains an increased valuesubstantially equal to that of the increased input force P, (A ,A,,) andthe additive metering spring force F,, the proportioning piston 26a isagain moved leftwardly toward its isolating position to reengage thevalve member 32a thereof with the seating member valve seat 33a to againisolate the increased fluid pressure P, from the increased output fluidpressure Por. It is, of course, obvious that the proportioning piston 26a will be responsive to further increases in the fluid pressure P, toeffect further correspondingly proportional increases in the outputfluid pressure For in the same manner as previously described.

When the master cylinder is de-actuated, the input fluid pressure? isvented to the atmosphere which effects de-energization of the frontbrake 4 and eliminates the input force P(A A acting on the proportioningpiston 26. Upon the elimination of the input force P(A -A,), the fluidpressure P, acting on the seating member 35 displaces the sealing lip 36thereof from sealing engagement with the housing counterbore 12 to openthe return flow passages 37 across said seating member, and in thismanner, the fluid pressure P, returns from the inlet chamber 380 throughthe connecting passage 25, the. outlet chamber 39, the open return flowpassages 37, the inlet chamber 38, the inlet port 23 and conduits 5,3 tothe master cylinder 2. When the fluid pressure P, is so reduced tocorrespondingly reduce the output force P,A to a value less than themetering spring force F,, the metering spring 31 moves the proportioningpiston 26 leftwardly to its original or inoperative position re-engagingthe stop 30 with the housing 9 and disengaging the valve member 32 fromthe seating member valve seat 33 to again open the seating memberaperture 34 reestablishing open pressure fluid communicationtherethrough between the inlet and outlet chambers 38, 39 to effectcomplete elimination of the fluid pressure P While the fluid pressure P,is being reduced to effect complete reduction of the output force P, Aon the proportioning piston 26, as described hereinabove, it is apparentthat such reduction of the fluid pressure P, also effects a simultaneouscorresponding reduction of the input force P,(A ,A acting on theproportioning piston 26a, and upon the elimination of the input forceP,(A ,-A the output fluid pressure Por acting on the seating member 35adisplaces the sealing lip 36a thereof from sealing engagement with thehousing counterbore 12a to open the seating member return flow passages37a. ln this manner, the fluid pressure Por returns from the rear brake8 through the conduit 7, and outlet port 24 of the control valve 6, theoutlet chamber 39a, the open return flow passage 37a of the seatingmember 35 into the inlet chamber 380 and therefrom to the mastercylinder 2, as previously described. When the fluid pressure Por is soreduced to correspondingly reduce the output force Por A to a value lessthan the metering spring force F,, the metering spring 31a moves theproportioning piston 26a rightwardly to its original positionre-engaging the stop 30a with the housing 9 and disengaging the valvemember 32 a from the seating member valve seat 33a to again open theseating member valve seat 33a to again open the seating member aperture34areestablishing open pressure fluid communication between the inletand outlet ports 23, 24 through the flow passage B to effect thecomplete elimination fluid pressure Por.

While the foregoing description of the system 1 and control valve 6illustrates the proportioning operation of the proportioning member 27to vary the fluid pressure immediately downstream thereof in response tothe fluid pressure immediately upstream thereof in the flow passage Bprior to the proportioning operation of the proportioning member 27a tovary the fluid pressure immediately downstream thereof in response tothe fluid pressure immediately upstream thereof in said flow passage, itis also contemplated that the proportioning operation of theproportioning member 27a can be, if desired, initiated prior to that ofthe proportioning member 27 by increasing the precompressive force F, ofthe metering spring 32a to a value predeterminately greater than theprecompressive force Fc of the metering spring 32 without substantiallyaltering the operating characteristics of the system 1 and control valve6.

From the foregoing, it is now apparent that a novel system 1 and controlvalve 6 are disclosed and that changes or modifications as to theprecise configurations, shapes, and details of the construction setforth in the disclosure by way of illustration may be made by thoseskilled in the art without departing from the spirit of the invention,

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A control valve comprising a housing having a pressure fluid flowpassage therethrough, a pair of proportioning members respectivelymovable in said flow passage in series flow relation for performingproportioning operations on the pressure fluid in said flow passage, oneof said proportioning members being initially movable in response tofluid pressure of a predetermined value toward a position in said flowpassage isolating the pressure fluid upstream thereof from thatdownstream thereof and being thereafter further movable in response toincreases in the fluid pressure upstream thereof toward a meteringposition effecting a metered increase in the fluid pressure downstreamthereof in one predetermined ratio with the increased fluid pressureupstream thereof, and the other of said proportioning members beinginitially movable in response to fluid pressure of another predeterminedvalue predeterminately different than the first named predeterminedvalue toward a position in said flow passage isolating the fluidpressure upstream thereof from that downstream thereof and beingthereafter further movable in response to increases in the fluidpressure upstream thereof toward a metering position effecting a meteredincrease in the fluid pressure downstream thereof in anotherpredetermined ratio predeterminately different than the first namedpredetermined ratio with the increased fluid pressure upstream thereof,and the metered fluid pressure of one of said one and otherproportioning members having a continuing and variable affect on themetered fluid pressure of the other of said one and other proportioningmembers wherein the metered fluid pressure acting on the downstream oneof said one and other proportioning members is a function of the productof the first named and other predetermined ratios.

2. A control valve according to claim 1, wherein one of said first namedand other predetermined ratios is greater than the other of said firstnamed and other predetermined ratios.

3. A control valve according to claim 1, wherein said one proportioningmember includes a proportioning piston movable in said housing, andresilient means engaged with said proportioning piston, saidproportioning piston being movable against the force of said resilientmeans toward its isolating position and the force of said resilientmeans assisting movement of said proportioning piston toward itsmetering position.

4. A control valve according to claim 1, wherein said otherproportioning member includes a proportioning piston movable in saidhousing, and resilient means engaged with said proportioning piston,said proportioning piston being movable against the force of saidresilient means toward its isolating position and the force of saidresilient means assisting movement of said proportioning piston towardits metering position.

5. A control valve according to claim 1, wherein said one and otherproportioning members include first and second proportioning pistonmeans slidable in said housing, and first and second spring meansengaged with said first and second piston means, the forces of saidfirst and second spring means opposing and assisting movement of saidfirst and second proportioning piston means toward their isolating andmetering positions, respectively.

6. A control valve according to claim 5, comprising first and secondvalve seats in said housing about said flow passage for engagement withsaid first and second proportioning piston means, said first and secondvalve seats being engaged by said first and second proportioning pistonmeans in their isolating positions and said first and secondproportioning piston means being disengaged from said first and secondvalve seats in their metering positions, respectively.

7. A control valve according to claim 6, comprising first and secondvalve means on said first and second proportioning piston means forengagement with said first and second valve seats, said first and secondvalve means being engaged with said first and second valve seats whensaid first and second proportioning piston means are in their isolatingpositions and disengaged therefrom when said first and secondproportioning piston means are in their metering positions,respectively.

8. A control valve according to claim 5, comprising first and secondpairs of opposed effective areas on said first and second proportioningpiston means subjected to fluid pressure immediately upstream anddownstream thereof in said flow passage, respectively, the fluidpressure immediately upstream of said first and second proportioningpiston means in excess of said first named and other predeterminedvalues acting on one of the areas of said first and second area pairs toassist said first and second spring means urging said first and secondproportioning piston means toward their metering positions and the fluidpressure immediately downstream of said first and second proportioningpiston means acting on the other of said areas of said first and secondarea pairs to oppose movement of said first and second proportioningpiston means to their metering positions, respectively.

9. A control valve comprising a housing having an inlet and outlet porttherein, proportioning means movable in said housing for controllingpressure fluid communication between said inlet and outlet ports, saidproportioning means being movable in response to fluid pressure at saidinlet port in excess of a predetermined value to effect metered pressurefluid communication between said inlet and outlet port and establish areduced fluid pressure at said outlet port in a predetermined ratio withthat at said inlet port, and other proportioning means movable in saidhousing in series flow relation with said first named proportioningmeans between said first named proportioning means and said outlet portfor controlling pressure fluid communication therebetween, said otherproportioning means being movable in response to the reduced fluidpressure of another predetermined value predetenninately in excess ofthe first named predetermined value to effect metered pressure fluidcommunication between said first named proportioning means and saidoutlet port to establish another reduced fluid pressure at said outletport in another predetermined ratio with the first named reduced. fluidpressure wherein the other reduced fluid pressure is a function of theproduct of the first named and other predetermined ratios.

10. A control valve comprising a housing, first inlet and outletchambers in said housing, a first proportioning member movable in saidhousing for controlling pressure fluid communication between said firstinlet and outlet chambers, said first proportioning member beinginitially movable in response to fluid pressure in said first inlet andoutlet chambers of a predetermined value toward a position isolatingsaid first inlet chamber from said first outlet chamber and beingthereafter further movable in response to increases in the fluidpressure in said first inlet chamber in excess of the predeterminedvalue toward a position effecting metered pressure fluid communicationbetween said first inlet and outlet chambers to establish fluid pressurein said first outlet chamber in a predetermined ratio with the increasedfluid pressure in said first inlet chamber, second inlet and outletchambers in said housing, means in said housing connecting said firstoutlet chamber in open pressure fluid communication with said secondinlet chamber, and a second proportioning member movable in said housingfor controlling pressure fluid communication between said second inletand outlet chambers, said second proportioning member being initiallymovable in response to the established fluid pressure in said firstoutlet chamber and said second inlet and outlet chambers of anotherpredetermined value different than the first named predetermined valuetoward a position isolating said second inlet chamber from said secondoutlet chamber and being thereafter further movable in response toincreases in the established fluid pressure in said first outlet chamberand said second inlet chamber in excess of the other predetermined valuetoward a position effecting metered pressure fluid communication betweensaid second inlet and outlet chambers to establish another fluidpressure in said second outlet chamber in another predetermined ratiowith the increased established fluid pressure in said first outletchamber and second inlet chamber wherein the fluid pressure establishedin said second outlet chamber is a function of the product of the firstnamed and other ratios.

11. In a hydraulic brake system having a fluid pressure responsivebrake, a master cylinder for establishing fluid pressure in said systemto energize said brake, and a pair of proportioning valve means in saidsystem in series flow relation for performing proportioning operationson the established fluid pressure in said system, said proportioningvalve means being generally operable in response to fluid pressuresimmediately upstream thereof of one and other predetermined values toreduce the fluid pressures immediately downstream thereof in said systemin one and other ratios respectively, wherein the reduced fluid pressureof the downstream one of said proportioning valve means is a function ofthe one and other ratios.

12. In a hydraulic brake system having at least one pressure supply andat least one pressure responsive brake, and a pair of proportioningvalves in series flow relation in said system with said proportioningvalves being operable generally for reducing the pressure from saidsupply to said brake under preselected conditions, one of saidproportioning valves being responsive to the pressure of said supply inexcess of a predetermined value to effect a reduced pressure through theother of said proportioning valves to said brake in a predeterminedratio with the pressure at said supply and said other proportioningvalve being responsive to the reduced pressure in excess of anotherpredetermined value predeterrninately in excess of the first namedpredetermined value to effect another reduced fluid pressure to saidbrake in another predetermined ratio with the first named reduced fluidpressure wherein the other reduced fluid pressure is a function of theproduct of the first named and other ratios.

13. In a hydraulic brake system having a pressure responsive brake and apressure supply for selectively pressurizing said brake, and a pair ofproportioning valves connected in series flow relation in said systemfor respectively controlling the application to said brakes of pressuresupplied from said supply under preselected conditions, one of saidproportioning valves being initially movable in response to the suppliedand applied pressures of a predetermined value toward a positionisolating said supply from the other of said proportioning valves andsaid brake and being thereafter further movable in response to increasesin the supplied pressure in excess of the predetermined value toward ametering position to effect of a metered increase in the pressureapplied through the other of said proportioning valves to said brake ina predetermined ratio with the increased supplied pressure and saidother proportioning valve being initially movable in response to thepressure applied from said one proportioning valve to said brake ofanother predetermined value predeterrninately in excess of the firstnamed predetermined value toward a position isolating said oneproportioning valve from said brake and being thereafter further movablein response to increases in the pressure applied from said oneproportioning valve in excess of the other predetermined value toward ametering position to effect a further metered increase in the pressureapplied to said brake in another predetermined ratio with the increasedpressure applied from said one proportioning valve wherein the fluidpressure applied to said brake is a function of the product of the firstnamed and other predetermined ratios.

14. In a hydraulic brake system having a pressure responsive brake, apressure supply in said system for selectively pressurizing said brake,and a device connected in said system between said supply and brake forcontrolling the application to said brakes of pressure supplied fromsaid supply under preselected conditions, said device comprising passagemeans connected with said supply and said brakes, a first proportioningvalve movable in said passage means in response to pressure appliedtherethrough from said supply to said brake of a predetermined valuetoward a position closing said passage means and being thereafterfurther movable in response to increases in the pressure from saidsource in excess of the predetermined value toward another position insaid passage means establishing metered communication therethroughbetween said supply and brake to effect a metered increase in thepressure applied to said brake in a predetermined ratio with theincreased pressure from said supply, and a second proportioning valvemovable in said passage means between said first proportioning valve andsaid brake, said second proportioning valve being movable in response tothe pressure applied therethrough from said first proportioning valve tosaid brake of another predetermined value predeterminately greater thanthe first named predetermined value toward a position closing saidpassage means and being thereafter further movable in response toincreases in the pressure from said first proportioning valve in excessof the other predetermined value toward another position in said passagemeans establishing metered communication therethrough between said firstproportioning valve and said brake to effect another metered increase inthe pressure applied to said brake in another predetermined ratio withthe increased pressure from said first proportioning valve wherein thevalue of the fluid pressure applied to said brake from said secondproportioning valve is a function of the product of the first named andother predetermined ratios.

15. A control valve comprising a housing having a pair of sets of inletand outlet chambers therein connected in series flow relation, and apair of proportioning members movable in said housing between the inletand outlet chambers of said chamber sets for performing fluid pressureproportioning operations therebetween under preselected conditions, saidproportioning members being operable generally in response to fluidpressures in excess of one and other predetermined values in said inletchambers of said chamber sets to reduce the fluid pressures in theoutlet chambers of said chamber sets in one and other predeterminedratios with the fluid pressures in said inlet chambers of said chambersets, respectively, and the reduced fluid pressure in one of the outletchambers of said chamber sets acting on one of said proportioningmembers having a continued and varying affect on the reduced fluidpressure in the other of the outlet chambers of said chamber sets actingon the other of said proportioning members wherein the reduced fluidpressure acting on the downstream one of said one and otherproportioning members is a function of the product of the one and otherratios.

16. A control valve comprising a housing having a pair of sets of inletand outlet chambers therein, a pair of proportioning members movable insaid housing between the inlet and outlet chambers of said chamber setsfor performing fluid pressure proportioning operations therebetween,respectively, said proportioning members being operable generally inresponse to the fluid pressures in said inlet chambers of said chambersets in excess of one and other predetermined values to reduce the fluidpressures in the outlet chambers of said chamber sets in one and otherpredetermined ratios with the fluid pressures in the inlet chambers ofsaid chamber sets, respectively, means in said housing connecting one ofthe outlet chambers of one of said chamber sets in pressure fluidcommunication with one of the inlet chambers of the other of saidchamber sets wherein the reduced fluid pressure in one of said one andthe other of said outlet chambers of said chamber sets acting on thedown-stream one of said proportioning members is a function of theproduct of the one and other ratios.

17. A control valve according to claim 16, wherein one of said one andother predetermined ratios is greater than the other thereof.

18. A control valve according to claim 16, wherein one of said one andother predetermined values is greater than the other thereof.

19. A control valve according to claim 16, wherein said proportioningmembers include a pair of resiliently urged means, said resilientlyurged means being movable against their own forces in response to thefluid pressures in said inlet and outlet chambers of said chamber setsof the one and other predetermined values toward positions isolatingsaid inlet and outlet chambers of said chamber sets and the forces ofsaid resiliently urged means thereafter assisting the fluid pressures inexcess of the one and other predetermined values in said inlet chambersof said chamber sets acting on said resiliently urged means to urge saidresiliently urged means toward a metering position effecting meteredpressure fluid communication between the inlet and outlet chambers ofsaid chamber sets and establishing metered fluid pressures in the outletchambers of said chamber sets in the one and other predetermined ratioswith the fluid pressures in the inlet chambers of said chamber sets,respectively.

20. A control valve according to claim 19, wherein said resilientlyurged means include a pair of proportioning pistons, and a pair ofresilient means engaged with proportioning pistons, said proportioningpistons being movable against the forces of said resilient means towardtheir isolating positions and the forces of said resilient means urgingsaid proportioning pistons toward their metering positions,respectively.

21. A control valve according to claim 20, comprising a pair of valveseats in said housing between said inlet and outlet chambers of saidchamber sets for engagement with said proportioning pistons, saidproportioning pistons being engaged with said valve seats in theirisolating positions and being disengaged from said valve seats in theirmetering positions, respectively.

22. A control valve according to claim 21, comprising a pair of valvemeans on said proportioning pistons for engagement with said valveseats, said valve means being engaged with said valve seats in theisolating positions of said proportioning pistons and being disengagedfrom said valve seats in the metering positions of said proportioningpistons, respectively.

23. A control valve according to claim 20, comprising a pair of opposedareas on said proportioning pistons subjected to the fluid pressures inthe inlet and outlet chambers of said chamber sets, respectively, thefluid pressures in excess of the one and other values in said inletchambers of said chamber sets acting on one of the opposed areas of saidproportioning pistons to assist said resilient means and urge saidproportioning pistons toward their metering positions and the fluidpressures in said outlet chambers of said chamber sets acting on theother of said opposed areas of said proportioning pistons to opposemovement thereof toward their metering positions, respectively.

24. A control valve according to claim 23, wherein said other area ofeach of said proportioning pistons is predeterminately greater than saidone area of each of said proportioning pistons.

25. A control valve comprising a housing having inlet and outlet portstherein, a pair of proportioning valves movable in said housing inseries flow relation between said inlet and outlet ports and operablegenerally to perform proportioning operations on pressure fluid flowfrom said inlet port to said outlet port under preselected conditions,respectively, each of said proportioning valves having inlet and outletsides, one of said proportioning valves being responsive to fluidpressure in excess of a predetermined value at one of said inlet portand the outlet side of the other of said proportioning valves toproportionally reduce the fluid pressure at one of said outlet ports andthe inlet side of said other proportioning valve in a predeterminedratio with the fluid pressure acting thereon in excess of thepredetermined value at the one of said inlet port and the outlet said ofsaid other proportioning valve, and said other proportioning valve beingresponsive to the fluid pressure in excess of another predeterminedvalue at one of said inlet port and the outlet side said oneproportioning valve to proportionally reduced the fluid pressure at oneof said outlet port and the inlet side of said one proportioning valvein another predetermined ratio with the fluid pressure acting thereon inexcess of the other predetermined value at the one of said inlet portand the outlet side of said one proportioning valve wherein the reducedfluid pressure acting on the downstream one of said one and otherproportioning valves is a function of the first named and other ratios.

26. A brake system comprising a brake, fluid pressure generating meansfor applying fluid pressure to said brake to effect energizationthereof, and a pair of proportioning valves connected in said system inseries flow relation between said generating means and said brake andoperable generally to perform proportioning operations on the appliedfluid pressure in said system under preselected conditions,respectively, one of said proportioning valves being responsive to thefluid pressure applied thereto in excess of a predetermined value fromone of said generating means and the other of said proportioning valvesto proportionally reduce in a predetermined ratio the fluid pressureapplied to one of said brake and said other proportioning valve, andsaid other proportioning valve being responsive to the fluid pressureapplied thereto in excess of another predetermined value from one ofsaid generating means and said one proportioning valve to proportionallyreduce in another predetermined ratio the fluid pressure applied to oneof said brake and said one proportioning valve wherein the reduced fluidpressure acting on the downstream one of said one and otherproportioning valve is a function of the product of said first named andother ratios.

27. A brake system comprising a brake, means for applying fluid pressureto said brake to effect energization thereof, and other means forcontrolling the application of the fluid pressure from said first namedmeans to said brake including a pressure fluid flow passage connectedbetween said first named means and said brake, and a pair ofproportioning valves movable in said flow passage in series flowrelation and operable generally in response to applied fluid pressureimmediately upstream thereof in excess of one and other differentpredetermined values in said flow passage to perform proportioningoperations thereon and establish reduced fluid pressures immediatelydownstream thereof in one and other predetermined ratios with the fluidpressures immediately upstream thereof, respectively, wherein thereduced fluid pressure acting on the downstream one of saidproportioning valves is a function of the product of the one and otherratios.

28. A fluid pressure system comprising at least one brake, means forapplying fluid pressure to said one brake to effect energizationthereof, and other means for controlling the fluid pressure applied fromsaid first named means to said one brake including a pair of sets ofinlet and outlet chambers in series flow relation, the inlet chamber ofone of said chamber sets being connected with said first named means andthe outlet chamber of the other of said chamber sets being connectedwith said one brake, and a pair of proportioning valves between theinlet and outlet chambers of said one and other chamber sets forperforming proportioning operations on the applied fluid pressure, saidproportioning valves being responsive to the applied fluid pressure inexcess of one and other predetermined values in the inlet chambers ofsaid one and other chamber sets to proportionally reduce the appliedfluid pressure in the outlet chambers of said one and other chamber setsin one and other predetermined ratios with the fluid pressures in excessof the one and other predetermined values in the inlet chambers of saidone and other chamber sets, respectively, wherein the reduced fluidpressure in the outlet chamber of said other chamber set is a functionof the product of the one and other ratios.

29. A fluid pressure system according to claim 28, comprising means insaid other means for connecting the inlet chamber of said other chamberset in pressure fluid communication with the outlet chamber of said onechamber set.

30. A control valve comprising a housing having a pressure fluid flowpassage therethrough, a pair of pro portioning valves movable in saidflow passage in series flow relation for performing proportioningoperations on the pressure fluid in said flow passage, saidproportioning valves being operable generally in response to fluidpressures immediately upstream thereof in excess of one and otherpredetermined values to establish reduced fluid pressures immediatelydownstream thereof in one and other predetermined ratios with the fluidpressures immediately upstream thereof in excess of the one and otherpredetermined values, respectively, and the reduced fluid pressureacting on one of said proportioning valves having a continued andvarying affect on the reduced output fluid pressure acting on the otherof said proportioning valves wherein the reduced fluid pressure actingon the downstream one of said one and other proportioning valves is afunction of the product of the one and other ratios.

UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTIIONR Patent No.3,697,138 e Issued October 10, 1972 Paul G. Marting It is certified thaterror appears in the above identified patent and that said LettersPatent are hereby corrected as shown below:

Column 4, line 2, "32" should read 31 line 44, "ration" should readratio line 47, I v "P0 (P (A A Fc/A should read P0 Column 5, line 15,delete the comma line 38, "33a" should read 32a line 39, "32a". shouldread 33a line 41, "For (Po(A -A F/A should read Po '(Ag -A Fs 2a shouldread-' Po(A -.-A line 50, delete to again open. the

-"- Por Column 6, line 31', "Po(A =A seating member valve seat 338Signed and sealed this I day of Signed and sealed this 1st day of May1973.

(SEAL) Attest:

EDWARD M. FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

1. A control valve comprising a housing having a pressure fluid flowpassage therethrough, a pair of proportioning members respectivelymovable in said flow passage in series flow relation for performingproportioning operations on the pressure fluid in said flow passage, oneof said proportioning members being initially movable in response tofluid pressure of a predetermined value toward a position in said flowpassage isolating the pressure fluid upstream thereof from thatdownstream thereof and being thereafter further movable in response toincreases in the fluid pressure upstream thereof toward a meteringposition effecting a metered increase in the fluid pressure downstreamthereof in one predetermined ratio with the increased fluid pressureupstream thereof, and the other of said proportioning members beinginitially movable in response to fluid pressure of another predeterminedvalue predeterminately different than the first named predeterminedvalue toward a position in said flow passage isolating the fluidpressure upstream thereof from that downstream thereof and beingthereafter further movable in response to increases in the fluidpressure upstream thereof toward a metering position effecting a meteredincrease in the fluid pressure downstream thereof in anotherpredetermined ratio predeterminately different than the first namedpredetermined ratio with the increased fluid pressure upstream thereof,and the metered fluid pressure of one of said one and otherproportioning members having a continuing and variable affect on themetered fluid pressure of the other of said one and other proportioningmembers wherein the metered fluid pressure acting on the downstream oneof said one and other proportioning members is a function of the productof the first named and other predetermined ratios.
 2. A control valveaccording to claim 1, wherein one of said first named and otherpredetermined ratios is greater than the other of said first named andother predetermined ratios.
 2. A control valve according to claim 1,wherein one of said first named and other predetermined ratios isgreater than the other of said first named and other predeterminedratios.
 3. A control valve according to claim 1, wherein said oneproportioning member includes a proportioning piston movable in saidhousing, and resilient means engaged with said proportioning piston,said proportioning piston being movable against the force of saidresilient means toward its isolating position and the force of saidresilient means assisting movement of said proportioning piston towardits metering position.
 4. A control valve according to claim 1, whereinsaid other proportioning member includes a proportioning piston movablein said housing, and resilient means engaged with said proportioningpiston, said proportioning piston being movable against the force ofsaid resilient means toward its isolating position and the force of saidresilient means assisting movement of said proportioning piston towardits metering position.
 5. A control valve according to claim 1, whereinsaid one and other proportioning members include first and secondproportioning piston means slidable in said housing, and first andsecond spring means engaged with said first and second piston means, theforces of said first and second spring means opposing and assistingmovement of said first and second proportioning piston means towardtheir isolating and metering positions, respectively.
 6. A control valveaccording to claim 5, comprising first and second valve seats in saidhousing about said flow passage for engagement with said first andsecond proportioning piston means, said first and second valve seatsbeing engaged by said first and second proportioning piston means intheir isolating positions and said first and second proportioning pistonmeans being disengaged from said first and second valve seats in theirmetering positions, respectivEly.
 7. A control valve according to claim6, comprising first and second valve means on said first and secondproportioning piston means for engagement with said first and secondvalve seats, said first and second valve means being engaged with saidfirst and second valve seats when said first and second proportioningpiston means are in their isolating positions and disengaged therefromwhen said first and second proportioning piston means are in theirmetering positions, respectively.
 8. A control valve according to claim5, comprising first and second pairs of opposed effective areas on saidfirst and second proportioning piston means subjected to fluid pressureimmediately upstream and downstream thereof in said flow passage,respectively, the fluid pressure immediately upstream of said first andsecond proportioning piston means in excess of said first named andother predetermined values acting on one of the areas of said first andsecond area pairs to assist said first and second spring means urgingsaid first and second proportioning piston means toward their meteringpositions and the fluid pressure immediately downstream of said firstand second proportioning piston means acting on the other of said areasof said first and second area pairs to oppose movement of said first andsecond proportioning piston means to their metering positions,respectively.
 9. A control valve comprising a housing having an inletand outlet port therein, proportioning means movable in said housing forcontrolling pressure fluid communication between said inlet and outletports, said proportioning means being movable in response to fluidpressure at said inlet port in excess of a predetermined value to effectmetered pressure fluid communication between said inlet and outlet portand establish a reduced fluid pressure at said outlet port in apredetermined ratio with that at said inlet port, and otherproportioning means movable in said housing in series flow relation withsaid first named proportioning means between said first namedproportioning means and said outlet port for controlling pressure fluidcommunication therebetween, said other proportioning means being movablein response to the reduced fluid pressure of another predetermined valuepredeterminately in excess of the first named predetermined value toeffect metered pressure fluid communication between said first namedproportioning means and said outlet port to establish another reducedfluid pressure at said outlet port in another predetermined ratio withthe first named reduced fluid pressure wherein the other reduced fluidpressure is a function of the product of the first named and otherpredetermined ratios.
 10. A control valve comprising a housing, firstinlet and outlet chambers in said housing, a first proportioning membermovable in said housing for controlling pressure fluid communicationbetween said first inlet and outlet chambers, said first proportioningmember being initially movable in response to fluid pressure in saidfirst inlet and outlet chambers of a predetermined value toward aposition isolating said first inlet chamber from said first outletchamber and being thereafter further movable in response to increases inthe fluid pressure in said first inlet chamber in excess of thepredetermined value toward a position effecting metered pressure fluidcommunication between said first inlet and outlet chambers to establishfluid pressure in said first outlet chamber in a predetermined ratiowith the increased fluid pressure in said first inlet chamber, secondinlet and outlet chambers in said housing, means in said housingconnecting said first outlet chamber in open pressure fluidcommunication with said second inlet chamber, and a second proportioningmember movable in said housing for controlling pressure fluidcommunication between said second inlet and outlet chambers, said secondproportioning member being initially movable in response to theestablished fluid pressure in said first outlet chamber aNd said secondinlet and outlet chambers of another predetermined value different thanthe first named predetermined value toward a position isolating saidsecond inlet chamber from said second outlet chamber and beingthereafter further movable in response to increases in the establishedfluid pressure in said first outlet chamber and said second inletchamber in excess of the other predetermined value toward a positioneffecting metered pressure fluid communication between said second inletand outlet chambers to establish another fluid pressure in said secondoutlet chamber in another predetermined ratio with the increasedestablished fluid pressure in said first outlet chamber and second inletchamber wherein the fluid pressure established in said second outletchamber is a function of the product of the first named and otherratios.
 11. In a hydraulic brake system having a fluid pressureresponsive brake, a master cylinder for establishing fluid pressure insaid system to energize said brake, and a pair of proportioning valvemeans in said system in series flow relation for performingproportioning operations on the established fluid pressure in saidsystem, said proportioning valve means being generally operable inresponse to fluid pressures immediately upstream thereof of one andother predetermined values to reduce the fluid pressures immediatelydownstream thereof in said system in one and other ratios respectively,wherein the reduced fluid pressure of the downstream one of saidproportioning valve means is a function of the one and other ratios. 12.In a hydraulic brake system having at least one pressure supply and atleast one pressure responsive brake, and a pair of proportioning valvesin series flow relation in said system with said proportioning valvesbeing operable generally for reducing the pressure from said supply tosaid brake under preselected conditions, one of said proportioningvalves being responsive to the pressure of said supply in excess of apredetermined value to effect a reduced pressure through the other ofsaid proportioning valves to said brake in a predetermined ratio withthe pressure at said supply and said other proportioning valve beingresponsive to the reduced pressure in excess of another predeterminedvalue predeterminately in excess of the first named predetermined valueto effect another reduced fluid pressure to said brake in anotherpredetermined ratio with the first named reduced fluid pressure whereinthe other reduced fluid pressure is a function of the product of thefirst named and other ratios.
 13. In a hydraulic brake system having apressure responsive brake and a pressure supply for selectivelypressurizing said brake, and a pair of proportioning valves connected inseries flow relation in said system for respectively controlling theapplication to said brakes of pressure supplied from said supply underpreselected conditions, one of said proportioning valves being initiallymovable in response to the supplied and applied pressures of apredetermined value toward a position isolating said supply from theother of said proportioning valves and said brake and being thereafterfurther movable in response to increases in the supplied pressure inexcess of the predetermined value toward a metering position to effectof a metered increase in the pressure applied through the other of saidproportioning valves to said brake in a predetermined ratio with theincreased supplied pressure and said other proportioning valve beinginitially movable in response to the pressure applied from said oneproportioning valve to said brake of another predetermined valuepredeterminately in excess of the first named predetermined value towarda position isolating said one proportioning valve from said brake andbeing thereafter further movable in response to increases in thepressure applied from said one proportioning valve in excess of theother predetermined value toward a metering position to effect a furthermetered increase in the pressure apPlied to said brake in anotherpredetermined ratio with the increased pressure applied from said oneproportioning valve wherein the fluid pressure applied to said brake isa function of the product of the first named and other predeterminedratios.
 14. In a hydraulic brake system having a pressure responsivebrake, a pressure supply in said system for selectively pressurizingsaid brake, and a device connected in said system between said supplyand brake for controlling the application to said brakes of pressuresupplied from said supply under preselected conditions, said devicecomprising passage means connected with said supply and said brakes, afirst proportioning valve movable in said passage means in response topressure applied therethrough from said supply to said brake of apredetermined value toward a position closing said passage means andbeing thereafter further movable in response to increases in thepressure from said source in excess of the predetermined value towardanother position in said passage means establishing meteredcommunication therethrough between said supply and brake to effect ametered increase in the pressure applied to said brake in apredetermined ratio with the increased pressure from said supply, and asecond proportioning valve movable in said passage means between saidfirst proportioning valve and said brake, said second proportioningvalve being movable in response to the pressure applied therethroughfrom said first proportioning valve to said brake of anotherpredetermined value predeterminately greater than the first namedpredetermined value toward a position closing said passage means andbeing thereafter further movable in response to increases in thepressure from said first proportioning valve in excess of the otherpredetermined value toward another position in said passage meansestablishing metered communication therethrough between said firstproportioning valve and said brake to effect another metered increase inthe pressure applied to said brake in another predetermined ratio withthe increased pressure from said first proportioning valve wherein thevalue of the fluid pressure applied to said brake from said secondproportioning valve is a function of the product of the first named andother predetermined ratios.
 15. A control valve comprising a housinghaving a pair of sets of inlet and outlet chambers therein connected inseries flow relation, and a pair of proportioning members movable insaid housing between the inlet and outlet chambers of said chamber setsfor performing fluid pressure proportioning operations therebetweenunder preselected conditions, said proportioning members being operablegenerally in response to fluid pressures in excess of one and otherpredetermined values in said inlet chambers of said chamber sets toreduce the fluid pressures in the outlet chambers of said chamber setsin one and other predetermined ratios with the fluid pressures in saidinlet chambers of said chamber sets, respectively, and the reduced fluidpressure in one of the outlet chambers of said chamber sets acting onone of said proportioning members having a continued and varying affecton the reduced fluid pressure in the other of the outlet chambers ofsaid chamber sets acting on the other of said proportioning memberswherein the reduced fluid pressure acting on the downstream one of saidone and other proportioning members is a function of the product of theone and other ratios.
 16. A control valve comprising a housing having apair of sets of inlet and outlet chambers therein, a pair ofproportioning members movable in said housing between the inlet andoutlet chambers of said chamber sets for performing fluid pressureproportioning operations therebetween, respectively, said proportioningmembers being operable generally in response to the fluid pressures insaid inlet chambers of said chamber sets in excess of one and otherpredetermined values to reduce the fluid pressures in the outletchambers of said chamber sets in one aNd other predetermined ratios withthe fluid pressures in the inlet chambers of said chamber sets,respectively, means in said housing connecting one of the outletchambers of one of said chamber sets in pressure fluid communicationwith one of the inlet chambers of the other of said chamber sets whereinthe reduced fluid pressure in one of said one and the other of saidoutlet chambers of said chamber sets acting on the down-stream one ofsaid proportioning members is a function of the product of the one andother ratios.
 17. A control valve according to claim 16, wherein one ofsaid one and other predetermined ratios is greater than the otherthereof.
 18. A control valve according to claim 16, wherein one of saidone and other predetermined values is greater than the other thereof.19. A control valve according to claim 16, wherein said proportioningmembers include a pair of resiliently urged means, said resilientlyurged means being movable against their own forces in response to thefluid pressures in said inlet and outlet chambers of said chamber setsof the one and other predetermined values toward positions isolatingsaid inlet and outlet chambers of said chamber sets and the forces ofsaid resiliently urged means thereafter assisting the fluid pressures inexcess of the one and other predetermined values in said inlet chambersof said chamber sets acting on said resiliently urged means to urge saidresiliently urged means toward a metering position effecting meteredpressure fluid communication between the inlet and outlet chambers ofsaid chamber sets and establishing metered fluid pressures in the outletchambers of said chamber sets in the one and other predetermined ratioswith the fluid pressures in the inlet chambers of said chamber sets,respectively.
 20. A control valve according to claim 19, wherein saidresiliently urged means include a pair of proportioning pistons, and apair of resilient means engaged with proportioning pistons, saidproportioning pistons being movable against the forces of said resilientmeans toward their isolating positions and the forces of said resilientmeans urging said proportioning pistons toward their metering positions,respectively.
 21. A control valve according to claim 20, comprising apair of valve seats in said housing between said inlet and outletchambers of said chamber sets for engagement with said proportioningpistons, said proportioning pistons being engaged with said valve seatsin their isolating positions and being disengaged from said valve seatsin their metering positions, respectively.
 22. A control valve accordingto claim 21, comprising a pair of valve means on said proportioningpistons for engagement with said valve seats, said valve means beingengaged with said valve seats in the isolating positions of saidproportioning pistons and being disengaged from said valve seats in themetering positions of said proportioning pistons, respectively.
 23. Acontrol valve according to claim 20, comprising a pair of opposed areason said proportioning pistons subjected to the fluid pressures in theinlet and outlet chambers of said chamber sets, respectively, the fluidpressures in excess of the one and other values in said inlet chambersof said chamber sets acting on one of the opposed areas of saidproportioning pistons to assist said resilient means and urge saidproportioning pistons toward their metering positions and the fluidpressures in said outlet chambers of said chamber sets acting on theother of said opposed areas of said proportioning pistons to opposemovement thereof toward their metering positions, respectively.
 24. Acontrol valve according to claim 23, wherein said other area of each ofsaid proportioning pistons is predeterminately greater than said onearea of each of said proportioning pistons.
 25. A control valvecomprising a housing having inlet and outlet ports therein, a pair ofproportioning valves movable in said housing in series flow relationbetween said inlet and outlet portS and operable generally to performproportioning operations on pressure fluid flow from said inlet port tosaid outlet port under preselected conditions, respectively, each ofsaid proportioning valves having inlet and outlet sides, one of saidproportioning valves being responsive to fluid pressure in excess of apredetermined value at one of said inlet port and the outlet side of theother of said proportioning valves to proportionally reduce the fluidpressure at one of said outlet ports and the inlet side of said otherproportioning valve in a predetermined ratio with the fluid pressureacting thereon in excess of the predetermined value at the one of saidinlet port and the outlet said of said other proportioning valve, andsaid other proportioning valve being responsive to the fluid pressure inexcess of another predetermined value at one of said inlet port and theoutlet side said one proportioning valve to proportionally reduced thefluid pressure at one of said outlet port and the inlet side of said oneproportioning valve in another predetermined ratio with the fluidpressure acting thereon in excess of the other predetermined value atthe one of said inlet port and the outlet side of said one proportioningvalve wherein the reduced fluid pressure acting on the downstream one ofsaid one and other proportioning valves is a function of the first namedand other ratios.
 26. A brake system comprising a brake, fluid pressuregenerating means for applying fluid pressure to said brake to effectenergization thereof, and a pair of proportioning valves connected insaid system in series flow relation between said generating means andsaid brake and operable generally to perform proportioning operations onthe applied fluid pressure in said system under preselected conditions,respectively, one of said proportioning valves being responsive to thefluid pressure applied thereto in excess of a predetermined value fromone of said generating means and the other of said proportioning valvesto proportionally reduce in a predetermined ratio the fluid pressureapplied to one of said brake and said other proportioning valve, andsaid other proportioning valve being responsive to the fluid pressureapplied thereto in excess of another predetermined value from one ofsaid generating means and said one proportioning valve to proportionallyreduce in another predetermined ratio the fluid pressure applied to oneof said brake and said one proportioning valve wherein the reduced fluidpressure acting on the downstream one of said one and otherproportioning valve is a function of the product of said first named andother ratios.
 27. A brake system comprising a brake, means for applyingfluid pressure to said brake to effect energization thereof, and othermeans for controlling the application of the fluid pressure from saidfirst named means to said brake including a pressure fluid flow passageconnected between said first named means and said brake, and a pair ofproportioning valves movable in said flow passage in series flowrelation and operable generally in response to applied fluid pressureimmediately upstream thereof in excess of one and other differentpredetermined values in said flow passage to perform proportioningoperations thereon and establish reduced fluid pressures immediatelydownstream thereof in one and other predetermined ratios with the fluidpressures immediately upstream thereof, respectively, wherein thereduced fluid pressure acting on the downstream one of saidproportioning valves is a function of the product of the one and otherratios.
 28. A fluid pressure system comprising at least one brake, meansfor applying fluid pressure to said one brake to effect energizationthereof, and other means for controlling the fluid pressure applied fromsaid first named means to said one brake including a pair of sets ofinlet and outlet chambers in series flow relation, the inlet chamber ofone of said chamber sets being connected with said first named means andthe outlet chamber of the other of said chamber sets being connectedwith said one brake, and a pair of proportioning valves between theinlet and outlet chambers of said one and other chamber sets forperforming proportioning operations on the applied fluid pressure, saidproportioning valves being responsive to the applied fluid pressure inexcess of one and other predetermined values in the inlet chambers ofsaid one and other chamber sets to proportionally reduce the appliedfluid pressure in the outlet chambers of said one and other chamber setsin one and other predetermined ratios with the fluid pressures in excessof the one and other predetermined values in the inlet chambers of saidone and other chamber sets, respectively, wherein the reduced fluidpressure in the outlet chamber of said other chamber set is a functionof the product of the one and other ratios.
 29. A fluid pressure systemaccording to claim 28, comprising means in said other means forconnecting the inlet chamber of said other chamber set in pressure fluidcommunication with the outlet chamber of said one chamber set.
 30. Acontrol valve comprising a housing having a pressure fluid flow passagetherethrough, a pair of proportioning valves movable in said flowpassage in series flow relation for performing proportioning operationson the pressure fluid in said flow passage, said proportioning valvesbeing operable generally in response to fluid pressures immediatelyupstream thereof in excess of one and other predetermined values toestablish reduced fluid pressures immediately downstream thereof in oneand other predetermined ratios with the fluid pressures immediatelyupstream thereof in excess of the one and other predetermined values,respectively, and the reduced fluid pressure acting on one of saidproportioning valves having a continued and varying affect on thereduced output fluid pressure acting on the other of said proportioningvalves wherein the reduced fluid pressure acting on the downstream oneof said one and other proportioning valves is a function of the productof the one and other ratios.